1. Field of the Invention
The present invention relates to an air suspension system, and, more particularly, to an air suspension system including a reduced number of valves and that is capable of minimizing the use of a compressor.
2. Description of the Related Art
Generally, a suspension does not simultaneously satisfy ride comfort and control stability. When the ride comfort is increased, the control stability decreases. When the control stability is increased, the ride comfort decreases. The reason is as follows. When springs of the suspension are soft, the springs easily absorb impacts generated due to an uneven load surface, and therefore, the ride comfort increases. However, a car body is unstable, and therefore, the control stability decreases. When springs of the suspension are hard, on the other hand, the control stability increases. However, the springs cannot sufficiently absorb impacts generated due to the unevenness of the load surface, and therefore, the ride comfort decreases. It is very difficult to change the strength of a conventional coil spring, which is made of steel. For this reason, an air spring using air has been developed. The air spring may be easily hardened or softened through the control of air pressure, if necessary. A suspension using such air springs is called an air suspension.
FIG. 1 is a view illustrating a conventional air suspension system.
Referring to FIG. 1, the conventional air suspension system includes a dryer 12 mounted on a compressed air pipe 11. A compressor outlet 13 is connected to a storage tank 14 via the dryer 12. Air is carried to the storage tank 14 from the atmosphere through an intake valve 15, a compressor 16, and the dryer 12. Also, compressed air is discharged from the storage tank 14 to the atmosphere through the dryer 12 and the intake valve 15. In this case, air flows in the direction opposite to the direction in which the air is charged from the atmosphere into the storage tank 14, whereby the satisfactory regeneration of the dryer 12 is guaranteed. Unexamined reference numeral 6 indicates a switching valve for controlling the flow direction of air, and unexamined reference numeral 17 indicates an opening and closing valve for controlling the outflow and inflow of air from and into an air spring 18. Also, unexamined reference numeral 7 indicates a check valve for preventing the backward flow of air, and unexamined reference numeral 8 indicates a throttle valve for increasing the flow speed of air.
In the air suspension system constructed as shown in FIG. 1, the number of the valves is large, whereby it is difficult to diagnose the breakdown of the valves, and the manufacturing costs of the air suspension system are great.
On the other hand, a two-way three-port valve, which controls the flow direction of air, may be used to restrain the excessive use of the valves. However, the two-way three-port valve has problems in that the power consumption of the two-way three-port valve is high, and the manufacturing costs of the two-way three-port valve are great.